Biogas: How the U.S. can Power 46 Million Homes with Energy from Food Scraps, Grass Clippings, and Feces

If the U.S. used all of their untapped organic ‘waste’ – humanure, livestock manure, dog & cat manure, grass clippings & leaves, and food waste – they would generate about $54.4 billion in clean Biogas energy every year, at no extra cost.

Biogas is a combustible gas mixture generated when organic matter, such as animal (and human) manure, food scraps, leaves, and grass clippings, are broken down by bacteria at warm temperatures (30-60°C) in an anaerobic environment (without oxygen).

When organic waste is fed into an anaerobic digester, it functions like a big concrete stomach, converting it into biogas, and rich garden fertilizer. Paul Sellew, CEO of Harvest Power Inc., said in a Boston Ted Talk that the compost derived from food waste his facility “improves the soil, has beneficial organisms that fight disease in soil, holds water to minimize irrigation, has micro and macronutrients, contains everything the plant needs to grow, is affordable, and locally available.”

Surprisingly, biogas has been used by humans for thousands of years. It was used to heat bath-water in 10th century Assyria, and in Persia during the 16th century AD. In Chinese literature the use of biogas dates back 2,000-3,000 years, and the Italian merchant traveller Marco Polo used to cover sewage ponds to produce bio-gas. It is estimated that there are currently 2 million bio-gas digesters operating in India, which many people use to power their homes.

Benefits of Biogas

Can be filtered, then compressed to make fuel for cars, buses, and trucks.

The end product is a nutrient-rich, odour-free fertilizer

Reduces greenhouse gas emissions

How Much Power can the U.S. Generate with Untapped Biogas?

Now let’s go on an adventure and calculate how much Biogas Americans are wasting each year in Landfills. We are going to do some simple math to find out first hand, approximately how much of the United States could be powered simply by tapping unused energy sources.

Humanure Potential Energy

Due to the efficiency of the human digestive system, the amount of biogas that can be yielded from human waste is limited in comparison with livestock manure and other feedstocks.

On average, one human produces 2.2 lbs (0.998kg) of urine and 0.5 lbs (0.227 kg) of fecal matter or a total of2.7lbs(1.224 kg) waste in one day.

Therefore, 51,379 homes can be powered completely by the energy generated from humanure in the United States.

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Animal Manure Potential Energy

Livestock Animals

According to the USDA,1.37 billiontons of solid animal waste produced every year in the U.S. This animal waste leeches into the environment and has devastating impact, polluting rivers, lakes, and estuaries across America.

Methane yield from manure varies depending on the animal, and their diets, but methane yield from pig manure has been assumed to be22m³per ton. Solid cow manure has a potential of40 m³of methane per ton. We’re going to meet somewhere in the middle and use 30m³ to calculate the potential energy that can be extracted from animal manure.

Therefore, almost 1 million homes (932,358) can be powered completely by the energy generated from dog & cat waste in the United States.

Grass Clippings and Leaves Potential Energy

Ordinary lawn clippings yield one of thehighest volumesof biogas per ton. One tonne of organic waste can produce125 cubic metresof methane, the energy equivalent of one barrel of oil. Every year we dispose of24 million tonsof leaves and grass clippings.

Therefore, almost 3 million homes (2,998,062) can be powered completely by the energy generated from the grass clippings and leaves that people throw out every year in the United States.

Food Waste Potential Energy

As of July 12, 2013, the United States is disposing of95%of their food waste in landfills and incinerators.

According to theEPA,“Over 36 million tons of food waste reach landfills each year in the United States”. Accounting for food waste in the home, restaurants, industrial food production, and grocery stores, all of this food that does not get eaten can be recycled and converted into energy using Biodigesters.

Total U.S. homes that can be powered completely using organic matter that is currently thrown in the garbage:46,051,837 homes

By adding up all of the kWh generated from the organic matter above, we find that in total, generating Biogas from these sources would generate 499,063,794,546 kWh of energy.

At the mid-peak time of day, hydro currently costs about10.9 centsper kWh.

499,063,794,546 kWh x 10.9 cents/kWh
= $54,397,953,605

Therefore, if the U.S. used all of their untapped organic matter – humanure, livestock manure, dog & cat manure, grass clippings & leaves, and food waste – they would generate about $54.4 billion in clean energy every year, for free.

How to Make Your Own Biogas Digester

The best part about a home Biogas digester is that, instead of being dependent on large corporations, you are in charge of your own energy production. “Just one cubic metre of biogas, says Li Xia, Deputy Director of the Guangxi Rural Energy Office in China, “can meet the daily energy needs of rural households, mainly for cooking 3 meals.”

Interesting Facts about Biogas

More than 500 landfill–to–energy projects are currently operating in the United States, and another 500 landfills are good candidates for turning their methane into an energy resource, which would produce enough electricity to power nearly 688,000 homes across the nation.

Germany, the 4th largest economy in world, recycles70%of its organic waste and has thousands of these facilities in operation.In 2009, Germany produced enough electricity from biogas to power 3.5 million homes.

Sweden has been operating a biogas-powered train since 2005. It shuttles passengers between two cities that are 75 miles apart.